MULTIPLICATION AND TRANSLOCATION OF XYLELLA-FASTIDIOSA IN PETIOLES AND STEMS OF GRAPEVINE RESISTANT, TOLERANT, AND SUSCEPTIBLE TO PIERCES DISEASE
Petioles of Vitis vinifera ‘French Colombard’ (susceptible to Pierce’s disease), and V. rotundifolia ‘Carlos’ (tolerant) and ‘Noble’ (resistant) were inoculated with virulent strain FC of Xylella fastidiosa. Populations of the bacterium increased rapidly in petioles of French Colombard but increased gradually in Carlos and Noble. Maximum populations were attained faster in French Colombard than in Carlos and Noble. X. fastidiosa rapidly colonized leaf veins of all cultivars. Stems of 5- and 7-wk-old plants were inoculated with strain FC or C of X. fastidiosa, and bacterial cfu/cm of stem 10, 20, and 50 cm above the inoculation point were determined over time. Both strains were translocated throughout French Colombard. The FC strain was reisolated at 50 cm in Carlos and 10 cm in Noble, 8 wk after 5-wk-old plants were inoculated. The C strain was not detected in Carlos or Noble. The FC strain was reisolated throughout Carlos and Noble, 8 wk after 7-wk-old plants were inoculated. The C strain was reisolated no higher than 10 cm above the inoculation point in Carlos and Noble.